1. Field of the Invention
The present invention relates generally to processing images of documents. More specifically, systems and methods using an unstructured pattern for three-dimensional model construction, such as may be used for processing images of documents are disclosed.
2. Description of Related Art
Scanning books, magazines, and other printed material into digital form has become more common with the advent of improved imaging, storage and distribution techniques. Although unbound printed material can generally be scanned with relative ease using automatic page-feeding mechanisms such as those commonly found on digital copiers and scanners, bound documents present additional challenges. Bound documents include not only books, but also periodicals, manuscripts, pamphlets, brochures, newspapers, manuals, and any other document having a bound edge. Many institutions, such as the libraries, universities, bookstores, and private enterprises have vast collections of bound documents. By converting these documents into electronic form, such institutions can reduce the cost of storage, facilitate remote access, enable simultaneous access by multiple users, facilitate search and retrieval of information, and/or protect information in rare or out-of-print works from loss or destruction.
Once the content of a bound document is scanned, the recorded image can be manipulated or otherwise processed. Digitally recorded bound documents can be reformatted, supplemented with additional information, compressed, and/or processed with OCR (optical character recognition) software, and indexed to facilitate electronic search. Thus, scanning and recording of bound documents facilitates the creation of digital libraries that can be remotely and simultaneously accessed and searched by multiple users.
Various mechanisms have been developed to enable the scanning of bound documents. For example, a traditional flat-bed platen scanner scans bound documents in a face-down position. However, for best results, a flat-bed scanner typically requires the application of force to the spine or binding region of the bound documents to insure that they come within the scanner's depth of focus. Such force can damage the spine region of the document. In addition, using the flat-bed platen can be tedious and time consuming, as the bound documents typically must be lifted and repositioned after each page is scanned. Further, image quality is often poor due to loss of focus, uneven illumination, and/or distortion caused by page curvature in the vicinity of the binding.
An alternative to the traditional flat-bed platen scanner is a platen-less scanner that captures image data from a bound document in a face-up position. Such scanners typically do not require application of additional stress to the binding region of a bound document, since the document is scanned in its natural, face-up position. Some such scanners make use of automatic page turning apparatuses.
Optics and software have been developed for compensating for the image distortion resulting from the inherently curved surfaces typical of open, edge-bound books that are not subjected to potentially damaging flattening pressure. For example, the curvature of a document's pages may be detected using a curvature detector, with a linear light source for defining a brightness distribution. The detected curves of the page can then be used to approximately rectify image signals received from the document scanner. Such platen-less scanning systems also often employ light sources to better illuminate the pages being imaged.
However, traditional three-dimensional model construction typically requires the detection of features in the three-dimensional object being viewed. Such features may include the edges of the curved pages and/or the gutter between two facing pages, for example. These features can often be difficult to detect and/or discriminate from other features. Thus, it would be desirable to provide systems and methods for improved three dimensional model construction.